Such a surge protector is already known from the common prior art. FIG. 1 shows such a surge protector, which has a main spark gap 2 comprising main electrodes 3. The main electrodes are connected in parallel with series capacitors, which are connected to a three-phase AC voltage system at a high-voltage potential. Owing to the bridging by means of the spark gap, the capacitor is protected against excessively high voltages. In this case, the series capacitors or other electronic components to be protected are arranged on a platform 4, which is set up in an insulated manner and is supported by means of supports in the form of columns (not illustrated in the figures) in an environment at ground potential. For example, the main electrode 3 illustrated at the bottom in FIG. 1 is therefore at a high-voltage potential, which corresponds to that of the platform 4, while the main electrode 3 illustrated at the top in FIG. 1 is at the high-voltage potential of the three-phase system. There is a voltage drop of between approximately 60 kV and 160 kV between the main electrodes, with the result that the components arranged on the platform 4 are designed for this voltage drop.
In order to actively trigger the spark gap 2, a trigger circuit 5 and a trigger electrode 6 are provided, the trigger circuit 5 having a capacitive voltage divider comprising a first capacitor 7 and a second capacitor 8. The second capacitor 8 can be bridged by a parallel branch, in which a tripping spark gap 9 and, connected in series with this tripping spark gap, a nonreactive resistor 10 are arranged. The tripping spark gap 9 can be moved over to its on position by means of control electronics 11, in which position a current flow via the parallel branch and thus bridging of the second capacitor 8 is made possible. Owing to the bridging, the trigger electrode 6 is connected to the potential of the lower main electrode 3, which is arranged physically closer to the upper main electrode 3 than the lower main electrode 3, however. A spark discharge results, which jumps over to the lower main electrode 3. The control electronics 11 can be supplied with the energy required for tripping the tripping spark gap 9 via an energy supply 12.
Triggering of the tripping spark gap 9 takes place actively. In this case, a protective device 13 monitors measured electrical variables of the three-phase system such as the alternating current of each phase of the three-phase system and/or the voltage drop across the electronic components on the platform 4. If tripping conditions are present, such as, for example, a threshold voltage at the component being exceeded, the protective device 13 generates a tripping signal, which is transmitted to a semiconductor laser 14, which thereupon generates an optical tripping signal, which is fed, via an optical waveguide 15, to the control electronics 11, as the reception unit. On reception of an optical tripping signal or in other words a trigger light, the control electronics cause the spark gap 2 to be tripped electrically.
The protective device 13 and the semiconductor laser 14 are at a ground potential, which makes it easier to gain access and simplifies maintenance, if required. The optical waveguide 15 makes it possible for the trigger light to be passed on safely, at the same time the insulation between the platform 4, which is at a high-voltage potential, and the components 13 and 14, which are at ground potential, of the surge protector 1 being maintained.
In particular owing to the electronics required with the energy supply on the platform 4, the previously known surge protector is cost-intensive and complex in terms of its maintenance.